Electrical stimulation of nerves and surrounding tissue is used to treat a variety of conditions. For example, electrical stimulation can be used to restore partial function to limbs or organs following traumatic injury. Electrical stimulation can also be used to reduce pain. Specifically, electrical stimulation can be used to treat disorders associated with the gastrointestinal (GI) system, such as, obesity and gastroesophageal reflux disease (GERD).
Obesity is a common condition and a major public health problem in developed nations including the United States of America. As of 2009, more than two thirds of American adults, approximately 127 million people, were either overweight or obese. Data suggest that 300,000 Americans die prematurely from obesity-related complications each year. Many children in the United States are also either overweight or obese. Hence, the overall number of overweight Americans is expected to rise in the future. It has been estimated that obesity costs the United States approximately $100 billion annually in direct and indirect health care expenses and in lost productivity. This trend is also apparent in many other developed countries.
For adults, the body mass index (BMI) is used to determine if one is overweight or obese. A person's BMI is calculated by multiplying body weight in pounds by 703 and then dividing the total by height in inches squared. A person's BMI is expressed as kilograms per meter squared. An adult is considered overweight if his or her BMI is between 25 and 30 kg/m2. Obesity is defined as possessing a BMI between 30 and 40 kg/m2. A BMI greater than 30 kg/m2 is associated with significant co-morbidities. Morbid obesity is defined as possessing either a body weight more than 100 pounds greater than ideal or a body mass index (BMI) greater than 40 kg/m2. Approximately 5% of the U.S. population meets at least one of the criteria for morbid obesity. Morbid obesity is associated with many diseases and disorders including, for example: diabetes; hypertension; heart attacks; strokes; dyslipidemia; sleep apnea; pickwickian syndrome; asthma; lower back and disc disease; weight-bearing osteoarthritis of the hips, knees, ankles and feet; thrombophlebitis and pulmonary emboli; intertriginous dermatitis; urinary stress incontinence; gastroesophageal reflux disease (GERD); gallstones; and, sclerosis and carcinoma of the liver. In women, infertility, cancer of the uterus, and cancer of the breast are also associated with morbid obesity. Taken together, the diseases associated with morbid obesity markedly reduce the odds of attaining an average lifespan. The sequelae raise annual mortality in affected people by a factor of 10 or more.
Gastro-esophageal reflux disease (GERD) is another common health problem and is expensive to manage in both primary and secondary care settings. This condition results from exposure of esophageal mucosa to gastric acid as the acid refluxes from the stomach into the esophagus. The acid damages the esophageal mucosa resulting in heartburn, ulcers, bleeding, and scarring, and long term complications such as Barrett's esophagus (pre-cancerous esophageal lining) and adeno-cancer of the esophagus.
Gastric electrical stimulation (GES) is aimed at treating both obesity and GERD. GES employs an implantable, pacemaker-like device to deliver low-level electrical stimulation to the gastrointestinal tract. For obesity, GES operates by disrupting the motility cycle and/or stimulating the enteric nervous system, thereby increasing the duration of satiety experienced by the patient. The procedure involves the surgeon suturing electrical leads to the outer lining of the stomach wall. The leads are then connected to the device, which is implanted just under the skin in the abdomen. Using an external programmer that communicates with the device, the surgeon establishes the level of electrical stimulation appropriate for the patient. The Abiliti® implantable gastric stimulation device, manufactured by IntraPace, is currently available in Europe for treatment of obesity.
In another example, Medtronic offers for sale and use the Enterra™ Therapy, which is indicated for the treatment of chronic nausea and vomiting associated with gastroparesis when conventional drug therapies are not effective. The Enterra™ Therapy uses mild electrical pulses to stimulate the stomach. According to Medtronic, this electrical stimulation helps control the symptoms associated with gastroparesis, including nausea and vomiting.
Electrical stimulation has also been suggested for use in the treatment of GERD, wherein the stimulation is supplied to the lower esophageal sphincter (LES). For example, in U.S. Pat. No. 6,901,295, assigned to the applicant of the current invention, “A method and apparatus for electrical stimulation of the lower esophageal sphincter (LES) is provided. Electrode sets are placed in the esophagus in an arrangement that induce contractions of the LES by electrical stimulation of the surrounding tissue and nerves. The electrical stimulus is applied by a pulse generator for periods of varying duration and varying frequency so as to produce the desired contractions. The treatment may be short-term or may continue throughout the life of the patient in order to achieve the desired therapeutic effect. The stimulating electrode sets can be used either alone or in conjunction with electrodes that sense esophageal peristalsis. The electrode sets can be placed endoscopically, surgically or radiologically.” The referenced invention relies on sensing certain physiological changes in the esophagus, such as changes in esophageal pH, to detect acid reflux. Once a change in esophageal pH is recognized, the system generates an electrical stimulation in an attempt to instantaneously close the LES and abort the episode of acid reflux. U.S. Pat. No. 6,901,295 is hereby incorporated by reference in its entirety.
Typically, the leads for LES stimulation are implanted in the lower esophageal wall using a laparoscopic approach. Lead implantation in the LES poses unique challenges different from implantation in any other part of the human body, including the stomach. One of the major challenges is the scarcity of space proximate the LES for the surgeon to maneuver. Another major challenge is exposure of the muscle tissue of the LES. The LES muscle tissue is covered by overlying fat tissue and the location of the gastroesophageal junction is difficult to identify. In addition, in a patient having a pre-existing gastrointestinal structural disorder, such as, a hiatal hernia, proper lead placement can be difficult to achieve. Often times the electrodes of the leads are not optimally positioned proximate the target tissue. Also, if a lead is not properly anchored, it can become dislodged and therapy will become ineffective. Therefore, what is needed is an effective and accurate method of implantation within the confined anatomy of the LES wherein the lead is securely fixed and/or anchored proximate the target tissue. What is also needed is an effective and accurate method of lead implantation that includes a hiatal closure as part of the implantation method.